Nickel chrome alloy



United States Patent Ofiiice 3,313,694 NHCKEL CHRUME ALLOY Arthur C. Heitmann, Newark, ()hio, assignor to Owens- Corning Fiberglass Corporation, a corporation of Delaware No Drawing. Filed Get. 30, 1963, tier. No. 319,970 8 Claims. (Cl. 75-171) This invention relates to a nickel chrome alloy for use at high temperatures. More particularly, the invention relates to an alloy composed primarily of nickel, but including substantial amounts of chromium, tungsten, iron, molybdenum, a metal from the group consisting of tantalum and columbium, and a controlled amount of carbon, and, in alloys which are to be cast, a controlled amount of silicon and manganese-the alloy being particularly suited for apparatus used in the production of glass fibers by a centrifugal process.

Glass fibers can be produced by the so-called rotary or centrifugal process, such as illustrated and disclosed by Slayter Patent No. 2,609,566 and other patents. Briefly stated, a rotary fiber forming process involves introducing a molten stream of glass at a temperature above its liquidus into a rotating centrifuge or spinner. The rotating centrifuge has peripheral orifices through which centrifugal force acting upon the rotating mass forces the molten glass to flow in small streams. The streams of glass are usually attenuated into fine fibers.

The spinner or centrifuge may have a generally cylindrical peripheral wall in which the orifices or holes are provided. Economical and practical commercial production rates can be achieved only when there are several thousand of such orifices in the spinner and only when the spinner is rotated at least several thousand revolutions per minute. Such a device operates at a temperature at least as high as 2000* F.

The alloy of the invention is particularly useful in the form of the aforementioned spinners, and is also useful generally in the glass industry for numerous high temperature service applications which require a high resistance to attack by both molten glass and air, a low creep, and a high load carrying ability at high temperatures.

It is an object of this invention to provide a new nickel chrome alloy which overcomes numerous shortcomings and disadvantages of previously known alloys, and which is of particular utility at high temperatures.

It is another object to provide a new nickel-chrome alloy which is highly resistant to attack by molten glass and air, which has low creep, and which has high load carrying ability at elevated temperatures.

It is still a further object to provide an alloy composed primarily of nickel but including substantial amounts of chromium, iron, tungsten, molybdenum, a metal from the group consisting of tantalum and columbium, and a limited carbon content plus controlled amounts of silica and manganese Where the alloy is to be cast. These, and other objects, will be readily apparent from the following detailed description which is intended only to illustrate and disclose the invention.

The nickel chrome alloy according to the invention consists essentially of certain balanced amounts of chromium, iron, tungsten, molybdenum, a metal from the group consisting of tantalum and columbium, and carbon, with the balance essentially nickel except for small amounts of certain other elements and minute amounts of impurities. The nickel chrome alloy comprises from 33 to 37 percent of chromium, 3 to 3 /2 *Unless expressly stated otherwise, all parts and percents herein and in the appended claims are expressed as parts and percents by weight.

percent of tungsten, 2 to 10 percent of iron, 1 to 3 percent of a metal for the group consisting of tantalum and columbium, 0.1 to 0.35 percent of carbon, 3 to 3 /2 percent of molybdenum, and the balance essentially nickel. To aid in casting the alloy, up to about 5 percent of silicon and up to about 5 percent manganese may be used. Preferably, the alloy includes from /2 percent to 1 /2 percent of silicon, and, most desirably, the alloy includes silicon in the indicated proportion and such an amount of manganese that the molal ratio of silicon to manganese is from 3:1 to 6:1. Minute amounts of other elements, such as boron, vanadium, aluminum, titanium may enhance the properties of the alloy.

The nickel-base alloy of the invention-has a composition upon analysis falling within the broad ranges set forth in the following Table I:

TABLE I Amount, percent by weight,

Composition: broad range Ni 45-55 Cr 33-37 W 3-3.5 Fe 2-10 C 0.1-0.35 Si 0-5 Mn 0-5 Mo 3-3 /2 Ta or Cb 1-5 The alloy of the invention may be prepared in accordance with recognized present-day melt procedures for nickel-base alloys. Desirably, the constituents used are in a pure state to avoid unwanted constituents and to control carefully the final alloy composition. It is preferred that most constituents be added in the form of relatively pure metals, although compounds or master alloys, such as ferrochromium, ferromanganese, ferrosilicon, and the like, may be used. Preferably, the melting is accomplished in a neutral crucible under an argon atmosphere. However, if desired, the charge, when in a molten state, may be protected by a slag of any known type suitable for nickel-base alloys. Other and additional constituents, such as additional charges of chomium, manganese, silicon, tungsten, molybdenum, tantalum, and the like, requisite to arrive at the desired alloy composition, then may be added when the melt temperature is about 2700 to 2800" F. Alternatively these elements may be added with the original charge of chromium and nickel. Heating is continued and, generally, the melt is between about 2.830 and 3000 F. when poured. A suitable scavenger may be added shortly before pouring to impart fluidity to the melt.

A desired article usually is made from the nickel-base alloy of the invention by casting. Such articles may be spinners, centrifuge buckets, bushing support frames, or

. the like. The alloy, as cast, can be welded and machined.

Example I A specific example of the alloy of the invention was prepared by the method described above. This alloy, by analysis, consisted essentially of the following weight percentages:

Nickel 52 Chromium 34.3 Iron 5.0 Tungsten 3.0 Molybdenum 3.0 Tantalum 1.0 Carbon 0,25 Silicon 1.25 Manganese 0.2

Patented May 9, 1967 The alloy was prepared according to the above procedure. Spinners for apparatus employed in producing glass fibers by the rotary process were cast and machined from the alloy. These spinners had an average outer diameter of about 8 inches with several thousand streamforming radial orifices in a vertical, generally cylindrical outer peripheral wall which was approximately 1% inches high, and /s to inch thick. The outer peripheral wall was supported by an upper conical wall which extended inwardly to a suitable means of attachment to a rotating quill of a rotary fiber forming apparatus. These spinners had a service life of from 80 to 140 hours, averaging 107 hours.

Alloy C By way of comparison but not according to the invention, spinners for the same machine but made from the following Alloy C had an average service life of approximately 90 hours:

Weight percent Nickel 62.45 Chromium 26.6 Tungsten 5.55 Iron 3.3 Carbon 0.25 Silicon 1.25 Manganese 1.1

The alloy of Example I produced according to the invention has very good resistance to corrosion by molten glass. A cast bar of the alloy when immersed in molten glass at 2200 F. for two hours had a weight loss of 0.3%. By way of comparison a cast bar of Alloy C had a weight loss of 0.7%.

Example II Another example of the alloy of the invention was prepared using the following weight percentages of metals prepared in the manner given above:

Nickel 52 Chromium 35 Iron 3.5 Tungsten 3.0 Molybdenum 3.0 Columbium 1.0 Carbon 0.25 Silicon 1.25 Manganese 1.0

A test bar of this alloy when immersed in molten glass at 2200" F. for two hours had a weight loss of 0.6%.

Example 111 Another example of an alloy of the invention was prepared using the following weight percentages of metals This alloy has less weight loss due to corrosion of molten glass than does Alloy C, and, in addition, has a greatly improved rupture life compared to that of Alloy C.

In general, the high chromium nickel and molybdenum are required to provide the necessary corrosion resistance. Iron in the matrix appears to add strength. Chromium, tungsten, tantalum and iron form carbides which when precipitated provide strength. Some of each of the tungsten, tantalum and iron must remain in the matrix. At

least about 0.1% carbon is necessary to form carbides. More than about 0.35% carbon causes too great a loss in ductility and results in spinner failures. Tantalum produces a random nonspherical carbide configuration. Columbium has an effect somewhat similar to tantalum, but the carbides formed tend to be spheroidized, so tantalum is preferred. The silicon and manganese are not required for strength or corrosion resistance, but need only be used where the metal is to be cast. For good casting properties the molal ratio of silicon to manganese should be at least 3:1 and not more than about 6:1, preferably about 5: 1.

The alloy of the invention provides a unique combination of desirable characteristics and properties. Preparation and evaluation of a number of experimental alloys containing more and less of the various alloying constituents has established that the particular, specified, limited and balanced amounts are necessary to realize the advantages of the invention. The superior service life and excellent corrosion resistance to glass of the alloy of the invention are believed to be provided by a unique balancing effect of the amounts of the various constituents therein. Metallographic studies and microstructural analysis of the alloy support this conclusion.

In general, the alloy comprises a dendritic network of complex carbides in an austentic matrix of nickel, chromium, iron and tungsten. The optimum carbon content for the alloy is about 0.25 percent. At the 0.25 percent carbon level the alloy microstructure exhibits a random, fine, non-spherical carbide precipitate uniformly dispersed. In contrast thereto, massive primary carbides and long continuous acicular carbide particles are found in alloys of somewhat higher carbon content. With lower carbon contents the precipitated carbide phase is finerand more randomly dispersed. From studies of the microstructures of experimental alloys of varied carbon contents it is apparent that the specified 0.1 to 0.35 percent carbon content results in the optimum amount of carbide forming elements of iron, chromium and tungsten being retained in the matrix phase of the alloy of the invention to provide mechanical strength and exceptional corrosion resistance at high temperatures. The presence of carbides in the structure strengthens the alloy in a manner similar to that of dispersion hardening. Optimum corrosion resistance to molten glass is obtained at the 0.25 percent carbon content where the alloy exhibits the discontinuous, fine carbide precipitate throughout. Higher carbon contents result in significantly increased corrosive attack. The matrix material is self-protecting with respect to air oxidation and relatively impervious to glass attack. However, if massive carbides extend to the surface, complete disintegration of such carbides is a consequence of glass corrosion. If such massive carbides form a continuous network around a matrix grain, that grain can be isolated by corrosion of the carbides and subjected to rapid erosive and corrosive attack on all sides.

Significant alterations in the amounts of the other constituent elements also result in noticeable detriment of some characteristics and properties even though some improvements may be obtained in other respects. A unique combination of characteristics and properties, which are desirable for high-temperature applications requiring mechanical strength and resistance to corrosive attack, is provided by the alloy of the invention.

It will be apparent that various changes and modifications can be made from the specific details set forth herein without departing from the spirit and scope of the attached claims.

What I claim is:

1. An alloy consisting essentially of:

Percent by weight said alloy being characterized by resistance to attack by molten glass, low creep, and high load carrying ability at elevated temperatures.

2. An alloy consisting essentially of:

Percent by weight Nickel 45-55 Chromium 33-37 Iron 2-10 Tungsten 3-3.5 Molybdenum 3-3.5 Carbon 0.1-0.35 Tantalum 1-3 Silicon, up to 1.5 Manganese, up to 1.0

said alloy being characterized by resistance to attack by molten glass, low creep, and high load carrying ability at elevated temperatures.

3. The alloy of claim 2 wherein both silicon and manganese are present in a silicon to manganese ratio between approximately 3:1 and 6: 1.

4. An alloy consisting essentially of:

Percent by weight, about said alloy being characterized by resistance to attack by molten glass, low creep, and high load carrying ability at elevated temperatures.

5. An alloy consisting essentially of:

Percent by weight, about Nickel 48 Chromium -u 35 Iron 8 Tungsten 3 Molybdenum 3 Tantalum 1 Carbon .25 Silicon 1.25 Manganese 0.25

said alloy being characterized by resistance to attack by molten glass, low creep, and high load carrying ability at elevated temperatures.

6. An alloy consisting essentially of:

Percent by weight Nickel 5 2 Chromium 35 Iron 3.5 Tungsten 3 .0 Molybdenum 3.0 Columbium 1.0 Carbon g 0.25 Silicon 1.25 Manganese 1.0

said alloy being characterized by resistance to attack by molten glass, low creep, and high load. carrying ability at elevated temperatures.

7. Glass processing apparatus of the type contacted by molten glass, said apparatus being formed from an alloy consisting essentially of the following percentages by weight: 33 to 37 percent of chromium, 3 to 3 /2 percent of tungsten, 2 to 10 percent of iron, 1 to 3 percent of a metal from the group consisting of tantalum and columbium, 0.1 to 0.35 percent of carbon, 3 to 3 /2 percent of molybdenum, and the balance essentially nickel.

8. Glass processing apparatus comprising a member having a plurality of openings theret-hrough through which molten glass passes to form tiny filaments of glass, said member being formed from an alloy consisting essentially of:

Percent by weight Nickel 45-55 Chromium 33-37 Iron 2-10 Tungsten 3-3.5 Molybdenum 3-3.5 Carbon 0.1-0.35 Tantalum 1-3 Silicon, up to 1.5 Manganese, up to 1.0

References Cited by the Examiner UNITED STATES PATENTS 2,587,275 2/1952 Bash 3 75171 2,607,170 8/1952 De Vries 75171 2,955,934 10/1960 Emery 75-171 3,031,717 5/1962 Levecque et al -15 FOREIGN PATENTS 547,402 10/1957 Canada.

HYLAND BIZOT, Primary Examiner.

WINSTON A. DOUGLAS, DAVID L. RECK,

Examiners.

C. M. SCHUTZMAN, R. O. DEAN, Assistant Examiners. 

1. AN ALLOY CONSISTING ESSENTIALLY OF: 